Such a spring is, for example, known from DE 10 2006 026 029 [U.S. Pat. No. 7,901,008]. A latch can lock or unlock the headrest part of a headrest in different height positions relative to the backrest of a vehicle seat. For the user to unlock it, a button is provided that is spring-loaded by a spring element. When the button is pressed, the spring element is loaded in such a way that restoring forces cause the button to return to its original position as soon as the button is no longer pressed.
In EP 2 608 988 [U.S. Pat. No. 9,004,602], an apparatus is also provided that can lock and unlock a headrest part at various height positions. The headrest has a pushbutton that is returned to its original position by a spring after pressing.
Such springs known from the aforementioned publications are commonly made of metal springs. These have the disadvantage that they vibrate after being pressed or due to shock vibration, when driving on a bumpy road for example, thereby causing undesired buzzing noises.